The 1985 FAO/WHO/UNU recommendations for energy and
protein requirements were based on a meeting of an expert panel held in October 1981 as
the culmination of a review process initiated soon after the publication of the 1973
guidelines (FAO/WHO/UNU, 1985). Since this time a considerable amount of new data have
been collected in the fields of pregnancy and lactation. Much of the research,
particularly with respect to pregnancy, has been specifically directed towards the
definition of recommended dietary allowances and therefore permits a thorough review of
the 1985 recommendations.

In this position paper we review the
new data in some detail, and attempt to resolve outstanding areas of controversy
especially those relating to the apparent mismatch between estimated incremental needs and
observed energy intakes. We explore alternative methods for expressing the incremental
requirements for reproduction to bring them closer into line with the use of physical
activity levels (PALs) as applied to other adults.

The existing FAO/WHO/UNU
recommendations for pregnancy and lactation are summarised in Tables 1 and 2 and compared
with some other recent guidelines from affluent nations.

Pregnancy

The 1985 values were based on a
general acceptance of Hytten's estimate that the total energy needs of pregnancy amount to
335 MJ (80000 kcal) or about 1.2 MJ/ day (285 kcal/day; Hytten & Chamberlain, 1980).
There was a clear recognition that this rather small increment could be greatly influenced
by possible changes in physical activity, and that a reduction in activity might explain
why 'many recent studies of food intakes of well nourished pregnant women indicate that
the extra energy requirements for tissue deposition are not always accompanied by
commensurate increases in intake'. The recommended increment of 1.2 MJ/day was applied
evenly across pregnancy because 'some fat should be deposited early in pregnancy, and
because appetite and periodic work requirements vary greatly'. It was considered
reasonable to reduce the average additional allowance to 0.84 MJ/day (200 kcal/day) where
healthy women reduce their activity. Table 1 highlights the wide differences in allowances
between various reports. These reflect both differences in interpretation of the available
data and in underlying philosophy. Most reports published after 1985 have recommended
lower increments than the FAO/WHO/UNU figure.

Correspondence: AM Prentice.

Lactation

The 1985 recommendations were based
on the median milk consumption of breast-fed Swedish infants for the first 6 months and on
more limited data from a number of populations for later periods. It was assumed that milk
energy was 2.9 kJ/g (0.7 kcal/g) and the efficiency of conversion of dietary to milk
energy was 80%. Furthermore it was assumed that the average woman would start lactation
with 150 MJ (36000 kcal) of additional fat reserves (laid down in pregnancy) and that
these would be used to subsidise the cost of lactation over the first 6 months thus
yielding about 0.84 MJ/day (200 kcal/day). It was stated that allowances 'will need to be
adjusted according to maternal fat stores and patterns of activity', but no additional
figures were provided.

It can be seen from Table 2 that
there is a much greater international consensus regarding recommended allowances for
lactation than for pregnancy (Table 1) There has not been such a pronounced trend towards
lowering allowances for lactation as there has been for pregnancy.

Recent advances in understanding
the links between maternal nutrition and the well-being of her offspring

Since 1985 there have been major
advances in our understanding of the potential influence that a mother's nutrition can
have on the health of her children. In particular, the work of Barker (1992) and his
colleagues on the fetal origins of adult disease has demonstrated that the pattern of
fetal growth is a strong predictor of later susceptibility to diseases of affluence such
as cardiovascular disease, non-insulin dependent diabetes, hypertension and
hyperlipidaemia (Goldberg & Prentice, 1994). These findings re-emphasise the
importance of ensuring optimal maternal nutrition, and indicate an urgent need to revise
the previous assumption that a pregnancy had been successful if it resulted in a baby of
viable birthweight. In our opinion such findings point to a need to err on the side of
plenty when setting allowances.

The trend towards reduced allowances
in pregnancy has been fuelled by the desire to ensure that recommended allowances are not
at variance with observations of increased food intake. The apparent paradox between
estimates of needs and estimates of intake has been explained away by assuming that
physical activity naturally decreases in pregnancy or that women are capable of
energy-sparing alterations in metabolism. We recommend that such arguments are introduced
only with great caution since women in developing countries may be prevented from reducing
their activity by the constraints of a subsistence livelihood. Furthermore it must be made
quite clear that, although energy-sparing metabolic adjustments may help women to carry a
pregnancy to term under harsh nutritional conditions, such adjustments almost certainly
result in health costs to both the mother and the baby. They should never be equated with
optimal performance. To this end we recommend that allowances should clearly reflect the
full costs of pregnancy and lactation, and that conditional reductions should receive less
prominence than in the past.